To bulk edit fields, make a field selection of either one or more fields. Select the edit button at the top of the page and start editing. You can edit the selected fields individually or make global changes to the selected fields.
They both duplicate fields. Clone just lets you select how many copies you want. Eg if you want to duplicate a field (or multiple fields) several times, then just select the field(s) and use clone. It will prompt for how many copies you want, then create that many in one go. Duplicate just does one duplicate of all selected fields at a time. Best idea is to create a test form – with Bulk Add Fields it’s easy– then save the form and switch to Bulk Actions. Then just play with the features.